Patients are stratified according to whether or not they are on a PI-containing antiretroviral regimen and the number of weeks of gestation (26 weeks or less versus greater than 26 weeks). Patients are followed at 8-week intervals from the time of entry until delivery or pregnancy termination, with an additional visit at 12 weeks after delivery or pregnancy termination. All infants born to study participants are evaluated at the time of delivery (anthropometrics and HIV DNA PCR) and are seen again at the mothers' 12-week post-delivery visit. Glucose tolerance testing and other metabolic studies are performed serially during pregnancy and again postpartum. This is an observational study and drugs are not supplied. Patients receiving antiretroviral therapy must obtain their own medications.